1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method which combine a plurality of images of different exposure amounts to generate combined image data.
2. Description of the Related Art
For example, in a scene in which there is a large difference between light and darkness, such as when outside scenery is viewed in sunny weather from a window, and indoor illumination is comparatively dark, if exposure is adjusted to match the outdoor scenery, in some cases the indoors will appear as a black dead area, while if the exposure is adjusted to match the indoor illumination, in some cases the outdoor scenery will undergo halation.
With respect to such kinds of scenes in which there is a large difference between light and darkness, to respond to a demand to obtain an image in which the gradations of both the indoors and the outdoor scenery are retained as much as possible, digital cameras have been proposed which adopt HDR combination technology that creates a combined image with a wider dynamic range (high dynamic range image) than a single image.
Such digital cameras photograph a plurality of images of differing exposure amounts, for example, a plurality of images including an image photographed under brighter exposure conditions than a proper exposure and an image photographed under darker exposure conditions than a proper exposure, and subjects the plurality of images of these different exposure amounts to HDR combination to generate combined image data.
White balance correction is performed with respect to the combined image data obtained in this manner, similarly to normal image data of a single photographed image. However, because a plurality of pieces of image data are the sources for generating the combined image data, proposals have been made with respect to which piece of image data to use as a basis for calculation of white balance coefficients.
For example, Japanese Patent Application Laid-Open Publication No. 2014-175734 discloses technology that, based on a predetermined condition, selects the evaluation result of which image among at least two images of different exposure amounts to use for calculating a white balance correction value.
In this connection, with respect to calculation of a white balance correction value in a single image, Japanese Patent Application Laid-Open Publication No. 2003-244723 describes technology that divides an image into a plurality of regions.